Orbitals and Energies #
Note – these are listed in BINDING ENERGY
Ca 2p ≈ 438 eV
Ca 2s ≈ 347 eV
Ca 3s ≈ 44 eV
Ca 3p ≈ 26 eV
Common Overlaps for Ca 2p #
Au 4d – Pd 3d – Ho 4p – Yb 4p – Th 4f – Zr 3p – Sm 4s – Ge LMM (Al Ka X-rays)
Theory and Background #
Calcium is crucial in materials science due to its role in structural materials, biomaterials, ceramics, and electronics. It is a key component in cement (CaO, CaCO₃), bioceramics like hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂), and functional materials such as CaF₂ for optics and CaTiO₃ for dielectrics.
Calcium compounds show subtle differences in binding energies and can therefore be slightly difficult to distinguish.
Experimental Advice #
Calcium is often seen as a contaminant on poorly handled samples. If calcium is found unexpectedly, it is possible the sample surface was touched without gloves on.
If recording a sample containing Mg, record the Ca 2s for quantification as Mg KLL overlaps with Ca 2p.
Data Analysis Guidance #
Calcium rarely exists in it’s metallic form, and as such typically peak shapes are found to be symmetric.
References #
- Powell, C. J. “Elemental binding energies for X-ray photoelectron spectroscopy.” Applied Surface Science 89.2 (1995): 141-149. Read it online here.
- Hanawa, Takao, and Mamoru Ota. “Calcium phosphate naturally formed on titanium in electrolyte solution.” Biomaterials 12.8 (1991): 767-774. Read it online here.
- Engelhard, Mark, and Don Baer. “Vacuum cleaved calcium carbonate by XPS.” Surface Science Spectra 6.2 (1999): 153-159. Read it online here.
- Briggs, David. “Handbook of X-ray and ultraviolet photoelectron spectroscopy.” (No Title) (1977). Read it online here.
